fix missing refmap troll in cached builds

[rfresh2]

Describe the pull
fix for refmap build issues like https://discord.com/channels/834570721070022687/841498080120668170/1060627048256770058

My method for reproducing:

1. wipe gradle cache
2. gradlew build -> check that its jar contains the refmap as expected
3. gradlew clean
4. gradlew build -> jar should no longer have refmap

Describe how this pull is helpful
lambda has gradle's local build cache enabled unlike most mods. this makes tasks like compileJava use their cached outputs unless there are actual class changes.

if you run the clean task, there are still task outputs that use cached values despite the build dir being wiped.
if you look at one of the bad compiled jars its missing lambda's refmap file entirely. and in the build dir the refmap is not present.

if i disable gradle build caching this issue doesn't occur (i.e. in gradle.properties).
Specifically only disabling build cache on compileJava seems sufficient to resolve this.

Additional context
https://docs.gradle.org/current/userguide/build_cache.html

[rfresh2]

Updated build to ForgeGradle 5 and fixed another reobf issue caused by configureReobf task running before mappings are generated

[Avanatiker]

This is strong! Thanks a lot for this :3